Suction structure in piston type compressor

ABSTRACT

A suction structure is provided for allowing refrigerant from a suction pressure region in a piston type compressor. The compressor includes a rotary valve. The suction structure includes a shifting device which shifts between a connecting state and a disconnecting state. In the connecting state an outlet of a supply passage of the rotary valve is connected to a suction pressure region and in the disconnecting state the outlet of the supply passage is disconnected from the suction pressure region. The shifting device includes a valve body, a return spring, and a permanent magnet. The valve body is movable between a connecting position and a disconnecting position. The return spring urges the valve body from the connecting position toward the disconnecting position. The permanent magnet attracts the valve body by magnetic force from the connecting position toward the disconnecting position.

BACKGROUND OF THE INVENTION

The present invention relates to a suction structure for allowing refrigerant from a suction pressure region in a piston type compressor. More specifically, the compressor has a rotary valve that is integrally rotated with a rotary shaft and that has a supply passage for introducing refrigerant from the suction pressure region into a compression chamber defined in a cylinder bore by a piston.

In piston type compressors, there are two types of suction valves. One is a rotary valve as disclosed in Unexamined Japanese Patent Publications No. 7-119631 and No. 2006-083835. The other is a reed type suction valve as disclosed in Unexamined Japanese Patent Publications No. 64-088064 and No. 2000-145629. The piston type compressors including the rotary valves has lower suction resistance in introducing refrigerant into cylinder bores, and has superior energy efficiency, compared to the piston type compressors including the reed type suction valves.

At the start of a conventional compressor disclosed in the above reference No. 7-119631, torque is rapidly increased in accordance with the compression of refrigerant gas, and is applied as a load to a vehicle engine (internal combustion). Thereby the vehicle speed is temporarily decreased at the start of the compressor, and the passengers of the vehicle feel start-up shock.

In the piston type compressor disclosed in the above reference No. 7-119631, the rotary valve is provided so as to be axially movable in the direction of the axis of the rotary shaft. The position of the rotary valve is displaced in accordance with the pressure supplied to a control pressure chamber. A bypass groove is formed in the rotary valve so as to communicate almost all the cylinder bores to a suction port formed at the center of a cylinder block. The rotary valve is located at a position in the axial direction of the rotary shaft in such a manner that almost all the cylinder bores are communicable with the suction port through the bypass groove at the stop and at the start of the compressor. Therefore, even when the piston performs compression of the refrigerant gas in the cylinder bore at the start of the compressor, the refrigerant gas in the cylinder bore is returned to the suction port through the bypass groove. The shock at the start of the compressor does not occur, accordingly.

In order to prevent leakage of the refrigerant gas along the periphery of the rotary valve, and also to allow the rotary valve to rotate, it is required that clearance around the periphery of the rotary valve is set as small as possible. However, with the structure in which the rotary valve is movable in the axial direction of the rotary shaft, the rotary valve needs clearance to allow the rotary valve to be movable in the axial direction of the rotary shaft. It is hard to set such clearance appropriately.

A compressor disclosed in Unexamined Japanese Patent Publication No. 2000-145629 includes a pressure differential detecting valve which is opened and closed in accordance with the pressure differential between discharge pressure and suction pressure. The pressure differential detecting valve is located between a low-pressure refrigerant passage for introducing refrigerant from the outside of the compressor and a suction chamber in the compressor. When the compressor is started in a state where the pressure in the compressor is balanced, the pressure differential detecting valve is closed, and the flow of the refrigerant from the outside of the compressor into the suction chamber is stopped. Thereby the shock at the start of the compressor is suppressed.

However, in the compressor disclosed in the reference No. 2000-145629, the refrigerant is remained in the suction chamber even when the pressure differential detecting valve is closed. The residual refrigerant is introduced into the cylinder bore and compressed therein. The volume of the suction chamber is set large so as to suppress the suction pulsation. Thereby large amount of refrigerant is introduced into the cylinder bore in a state where the pressure differential detecting valve is closed, and the effect in suppressing the shock at the start of the compressor is not sufficiently obtained.

The present invention is directed to increase the effect in suppressing the shock at the start of the compressor.

SUMMARY OF THE INVENTION

In accordance with the present invention, a suction structure is provided for allowing refrigerant from a suction pressure region in a piston type compressor. The compressor has cylinder bores arranged around a rotary shaft for accommodating a respective piston. A cam body is formed with the rotary shaft. The piston is engaged with the cam body so that rotation of the rotary shaft is transmitted to the piston. A compression chamber is defined by the piston in the respective cylinder bore. A rotary valve has a supply passage for introducing the refrigerant from the suction pressure region to the compression chamber. The rotary valve is rotated integrally with the rotary shaft. The suction structure includes a shifting device. The shifting device shifts between a connecting state and a disconnecting state. In the connecting state the outlet of the supply passage is connected to the suction pressure region and in the disconnecting state the outlet of the supply passage is disconnected from the suction pressure region. The shifting device includes a valve body, a return spring, and a permanent magnet. The valve body is movable between a connecting position and a disconnecting position. The connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state. The return spring urges the valve body from the connecting position toward the disconnecting position. The permanent magnet attracts the valve body by magnetic force from the connecting position toward the disconnecting position.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a longitudinal cross-sectional view of a compressor according to a first preferred embodiment of the present invention;

FIG. 2A is a cross-sectional view which is taken along the line I-I in FIG. 1;

FIG. 2B is a cross-sectional view which is taken along the line II-II in FIG. 1;

FIG. 3 is a partially enlarged cross-sectional view illustrating the suction structure of the compressor in a disconnecting state according to the first preferred embodiment of the present invention;

FIG. 4 is a partially enlarged cross-sectional view illustrating the suction structure of the compressor in a connecting state according to the first preferred embodiment of the present invention;

FIG. 5A is a graph showing torque fluctuation of the compressor having a permanent magnet according to the first preferred embodiment of the present invention;

FIG. 5B is a graph showing positional change of a valve body in the compressor having the permanent magnet according to the first preferred embodiment of the present invention;

FIG. 5C is a graph showing torque fluctuation of a piston type compressor without the permanent magnet;

FIG. 5D is a graph showing positional change of a valve body in the piston type compressor without the permanent magnet;

FIG. 6A is a partially enlarged cross-sectional view of a compressor illustrating a suction structure in a disconnecting state according to a second preferred embodiment of the present invention;

FIG. 6B is a partially enlarged cross-sectional view of the compressor illustrating the suction structure in a connecting state according to the second preferred embodiment of the present invention;

FIG. 7A is a partially enlarged cross-sectional view of a compressor illustrating a suction structure in a connecting state according to a third preferred embodiment of the present invention;

FIG. 7B is a partially enlarged cross-sectional view of the compressor illustrating the suction structure in a disconnecting state according to the third preferred embodiment of the present invention;

FIG. 8A is a partially enlarged cross-sectional view of a compressor illustrating a suction structure in a disconnecting state according to a fourth preferred embodiment of the present invention;

FIG. 8B is a partially enlarged cross-sectional view of the compressor illustrating the suction structure in a connecting state according to the fourth preferred embodiment of the present invention; and

FIG. 9 is a longitudinal cross-sectional view of a compressor according to a fifth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first preferred embodiment of a piston type compressor 10 according to the present invention will now be described with reference to FIGS. 1 through 5. The compressor 10 is a fixed displacement type. It is noted that the front side and the rear side of the compressor 10 respectively correspond to the left side and the right side in the drawings. Referring to FIG. 1, a front cylinder block 11 is connected to a rear cylinder block 12. A front housing 13 is connected to the front cylinder block 11. A rear housing 14 is connected to the rear cylinder block 12. The front and rear cylinder blocks 11, 12 and the front and rear housings 13, 14 constitute a whole compressor housing assembly of the piston type compressor 10. A discharge chamber 131 as a discharge pressure region in the compressor 10 is defined in the front housing 13. A discharge chamber 141 as a discharge pressure region in the compressor 10 is defined in the rear housing 14. A suction chamber 142 as a suction pressure region is defined in the rear housing 14. It is noted that “in the compressor” corresponds to the inside of the whole compressor housing assembly, and that “out of the compressor” corresponds to the outside of the whole compressor housing assembly.

A valve port plate 15, a valve plate 16 and a retainer plate 17 are interposed between the front cylinder block 11 and the front housing 13. A valve port plate 18, a valve plate 19 and a retainer plate 20 are interposed between the rear cylinder block 12 and the rear housing 14. Discharge ports 151, 181 are respectively formed in the valve port plates 15, 18. Discharge valves 161, 191 are respectively formed in the valve plates 16, 19 to open and close the respective discharge ports 151, 181. Retainers 171, 201 are respectively formed in the retainer plates 17, 20 to regulate the respective opening degrees of the discharge valves 161, 191.

A rotary shaft 21 is rotatably supported by the front and rear cylinder blocks 11, 12 and is inserted into shaft holes 111, 121 which extend through the front and rear cylinder blocks 11, 12. The outer periphery of the rotary shaft 21 is in contact with the inner periphery of the shaft holes 111, 121. The rotary shaft 21 is directly supported by the front and rear cylinder blocks 11, 12 through the inner periphery of the respective shaft holes 111 and 121. A contacting portion of the outer periphery of the rotary shaft 21 with the shaft hole 111 forms a sealing circumferential surface 211. A contacting portion of the outer periphery of the rotary shaft 21 with the shaft hole 121 forms a sealing circumferential surface 212.

A swash plate 23 as a cam body is secured to the rotary shaft 21. The swash plate 23 is accommodated in a crank chamber 24 which is defined between the front and rear cylinder blocks 11, 12. A lip-seal type shaft seal member 22 is interposed between the front housing 13 and the rotary shaft 21. The shaft seal member 22 prevents leakage of the refrigerant gas through the clearance between the front housing 13 and rotary shaft 21. The front end of the rotary shaft 21 protruding externally from the front housing 13 is connected to a vehicle engine 26 as an external drive source through an electromagnetic clutch 25. The rotary shaft 21 receives driving force for rotation from the vehicle engine 26 through the electromagnetic clutch 25.

As shown in FIG. 2A, a plurality of front cylinder bores 27 is formed in the front cylinder block 11 and is arranged around the rotary shaft 21. As shown in FIG. 2B, a plurality of rear cylinder bores 28 is formed in the rear cylinder block 12 and is arranged around the rotary shaft 21. Front and rear heads of a double-headed piston 29 are respectively accommodated in the pair of the cylinder bores 27, 28.

As shown in FIG. 1, the double-headed piston 29 is engaged with the swash plate 23 through a pair of shoes 30. The swash plate 23 integrally rotates with the rotary shaft 21. The rotary motion of the swash plate 23 is transmitted to the double-headed piston 29 through the shoes 30 so that the double-headed piston 29 reciprocates in the pair of the cylinder bores 27, 28. Compression chambers 271, 281 are defined in the respective cylinder bores 27, 28.

An in-shaft passage 31 is formed in the rotary shaft 21. The in-shaft passage 31 extends along the rotary axis 210 of the rotary shaft 21. An inlet 311 of the in-shaft passage 31 is formed at an end surface 213 of the rotary shaft 21 in the cylinder block 12. The inlet 311 is open to the suction chamber 142 in the rear housing 14. A front outlet 312 of the in-shaft passage 31 is open at the front sealing circumferential surface 211 of the rotary shaft 21 in the shaft hole 111. A rear outlet 313 of the in-shaft passage 31 is open at the rear sealing circumferential surface 212 of the rotary shaft 21 in the shaft hole 121.

As shown in FIG. 2A, a front communication passage 32 is formed in the front cylinder block 11 so as to communicate with the cylinder bore 27 and the shaft hole 111. As shown in FIG. 2B, a rear communication passage 33 is formed in the rear cylinder block 12 so as to communicate with the cylinder bore 28 and the shaft hole 121. As the rotary shaft 21 rotates, the outlets 312, 313 of the in-shaft passage 31 intermittently communicate with the communication passages 32, 33.

When the front cylinder bore 27 is in a suction process, that is, when the double-headed piston 29 moves from the left side to the right side in FIG. 1, the outlet 312 communicates with the communication passage 32. As a result, refrigerant in the in-shaft passage 31 is introduced into the compression chamber 271 in the cylinder bore 27 through the outlet 312 and the communication passage 32.

When the front cylinder bore 27 is in a discharge process, that is, when the double-headed piston 29 moves from the right side to the left side in FIG. 1, the outlet 312 is disconnected from the communication passage 32. As a result, refrigerant in the compression chamber 271 is discharged to the discharge chamber 131 through the discharge port 151 by pushing the discharge valve 161 away. The refrigerant discharged to the discharge chamber 131 flows out to an external refrigerant circuit 34 through a passage 341.

When the rear cylinder bore 28 is in a suction process, that is, in a process of the double-headed piston 29 moving from the right side to the left side in FIG. 1, the outlet 313 communicates with the communication passage 33. As a result, refrigerant in the in-shaft passage 31 of the rotary shaft 21 is introduced into the compression chamber 281 of the cylinder bore 28 through the outlet 313 and the communication passage 33.

When the rear cylinder bore 28 is in a discharge process, that is, in a process of the double-headed piston 29 moving from the left side to the right side in FIG. 1, the outlet 313 is disconnected from the communication passage 33. As a result, refrigerant in the compression chamber 281 is discharged to the discharge chamber 141 through the discharge port 181 by pushing the discharge valve 191 away. The refrigerant discharged to the discharge chamber 141 flows out to the external refrigerant circuit 34 through a passage 342.

The external refrigerant circuit 34 is provided with a heat exchanger 37 for removing heat from refrigerant, an expansion valve 38, and a heat exchanger 39 for evaporating the refrigerant with heat. The expansion valve 38 controls the flow rate of the refrigerant in accordance with the fluctuation in temperature of the gaseous refrigerant at the outlet of the heat exchanger 39. The refrigerant flowing out to the external refrigerant circuit 34 returns to the suction chamber 142.

The part of the rotary shaft 21 corresponding to the sealing circumferential surface 211 forms a first rotary valve 35. The part of the rotary shaft 21 corresponding to the sealing circumferential surface 212 forms a second rotary valve 36. The rotary valves 35, 36 serve as a valve mechanism which is disposed adjacent to the compression chambers 271, 281 in this embodiment. The rotary valves 35, 36 are formed integrally with the rotary shaft 21. That is, the rotary shaft 21 serves as rotary valves. The rotary axis 210 serves as the rotary axis of the rotary valves. The end surface 213 of the rotary shaft 21 (the end surface of the rotary valve) intersects with the rotary axis 210 of the rotary valves. The in-shaft passage 31 and outlets 312, 313 form the supply passage of the rotary valves 35, 36. The shaft hole 111 serves as a valve accommodation chamber for accommodating the first rotary valve 35, and the shaft hole 121 serves as a valve accommodation chamber for accommodating the second rotary valve 36.

As shown in FIGS. 3 and 4, a base portion 40 is formed integrally with the end wall of the rear housing 14. An inner wall of the rear housing 14 defines the suction chamber 142. A cylindrical portion 41 is formed integrally with the inner wall surface 401 of the base portion 40. The rotary axis 210 of the rotary shaft 21 intersects with the inner wall surface 401 perpendicularly.

A valve body 42 in the form of a spool is slidably inserted in the inner space 411 inside of the cylindrical portion 41. The valve body 42 is formed of magnetic material. The valve body 42 includes a disk-like piston member 43 and a cylindrical member 44. An introduction port 441 is open at the outer peripheral surface of the cylindrical member 44. The introduction port 441 communicates with the inner space 442 inside of the cylindrical member 44. The inner space 442 serves as an inner passage of the valve body 42. The piston member 43 defines a pressure chamber 412 in the inner space 411 inside of the cylindrical portion 41. The pressure chamber 412 communicates with the suction chamber 142 through a hole 413.

A guide cylinder 45 is formed integrally with the end surface of the rear cylinder block 12 adjacent to the rear housing 14 so as to face to the cylindrical portion 41. The inner space 451 of the guide cylinder 45 communicates with the inlet 311 of the in-shaft passage 31 of the rotary shaft 21. The rear end of the guide cylinder 45 and the front end of the cylindrical portion 41 are spaced apart from each other, and the cylindrical member 44 of the valve body 42 is slidably fitted together by insertion with the guide cylinder 45. A circular clip 46 is attached to the inner circumferential surface of the guide cylinder 45. A return spring 47 is interposed between the circular clip 46 and the piston member 43. The return spring 47 urges the valve body 42 so that the valve body 42 approaches the base portion 40. When the valve body 42 approaches the base portion 40, the volume of the pressure chamber 412 decreases.

In the inner space 411 of the cylindrical portion 41, a permanent magnet 48 is fixed to the inner wall surface 401 of the base portion 40. The permanent magnet 48 protrudes from the inner wall surface 401 in the inner space 411 so that the piston member 43 is capable of coming into surface contact with the permanent magnet 48.

In the state shown in FIG. 4, the introduction port 441 is in a position where the entire introduction port 441 is exposed to the suction chamber 142. The in-shaft passage 31 communicates with the suction chamber 142 through the inner space 451 of the guide cylinder 45, the inner space 442 of the cylindrical portion 44 and the introduction port 441. In this state, the valve body 42 is spaced apart from the permanent magnet 48, and FIG. 4 shows a state where the valve body 42 is in a position to connect the in-shaft passage 31 to the suction chamber 142. In a state shown in FIG. 3, the introduction port 441 is in a position where the entire introduction port 441 is fitted in the inner space 411, and the in-shaft passage 31 is disconnected from the suction chamber 142. In this state, the valve body 42 is in surface contact with the permanent magnet 48, and FIG. 3 shows a state where the valve body 42 is in a position to disconnect the in-shaft passage 31 from the suction chamber 142.

As shown in FIG. 1, the activation of the electromagnetic clutch 25 is controlled by a computer C. The computer C is connected by way of signals to an operating switch 49 for an air conditioner, a room temperature setting device 50 for setting a target room temperature, and a room temperature detecting device 51 for detecting a room temperature. When the operating switch 49 is turned on, the computer C controls the electric supply (activation and deactivation) to the electromagnetic clutch 25 in accordance with the temperature difference between the target room temperature and the detected room temperature.

The computer C shuts off the electric supply to the electromagnetic clutch 25, when the detected temperature is lower than the target temperature, or, when the detected temperature is higher than the target temperature and the temperature difference is within an allowable range. In this case, the electromagnetic clutch 25 is in a disconnected state, and the driving force of the vehicle engine 26 is not transmitted to the rotary shaft 21. The computer C supplies electric current to the electromagnetic clutch 25, when the detected temperature is higher than the target temperature and the temperature difference between the detected temperature and the target temperature is beyond the allowable level. In this case, the electromagnetic clutch 25 is in a connected state, and the driving force of the vehicle engine 26 is transmitted to the rotary shaft 21.

When the operation of the compressor 10 is shut down (the electromagnetic clutch 25 is in a disconnected state), the pressure in the compressor 10 is balanced. In this state, the valve body 42 is in the disconnecting position by the spring force of the return spring 47, as shown in FIG. 3. When the compressor 10 is started, the refrigerant in the in-shaft passage 31 and the inner spaces 451, 442 is introduced into the compression chambers 271 (as shown in FIG. 1) and 281. Due to the suction motion, the pressures in the in-shaft passage 31 and the inner spaces 451, 442 are decreased. That is, the pressures in the in-shaft passage 31 and the inner spaces 451, 442 become lower than the pressure in the suction chamber 142. The pressure in the suction chamber 142 is applied to the pressure chamber 412, and the pressure in the pressure chambers 412 corresponds to the pressure in the suction chamber 142. The pressure in the pressure chamber 412 opposes to the pressure in the inner spaces 451, 442 and the spring force of the return spring 47 through the valve body 42.

The sum of the spring force of the return spring 47 and the magnetic force of the permanent magnet 48 is set to be overcome by the pressure difference between the pressure chamber 412 and the inner spaces 451, 442 when the compressor 10 is operated. When the compressor 10 is started in a state where the valve body 42 is in contact with the permanent magnet 48, the pressure difference between the pressure chamber 412 and the inner spaces 451, 442 overcomes the sum of the spring force of the return spring 47 and the magnetic force of the permanent magnet 48. Thereby the valve body 42 is moved from the disconnecting position as shown in FIG. 3 to the connecting position as shown in FIG. 4. When the valve body 42 is in the connecting position, the refrigerant in the suction chamber 142 flows into the compression chambers 271, 281 through the introduction port 441, inner spaces 442, 451, in-shaft passage 31 and the communication passages 32, 33.

When the operation of the compressor 10 is stopped, the refrigerant in the in-shaft passage 31 and the inner spaces 451, 442 is not introduced into the compression chambers 271 (as shown in FIG. 1) and 281. Thereby the pressures in the in-shaft passage 31 and the inner spaces 451, 442 are increased. Therefore, the pressures in the in-shaft passage 31 and the inner spaces 451, 442 are balanced with the pressure in the pressure chamber 412. Accordingly the valve body 42 is moved from the connecting position as shown in FIG. 4 to the disconnecting position as shown in FIG. 3 due to the spring force of the return spring 47.

The valve body 42 is moved between the connecting position and the disconnecting position in accordance with the pressure in the supply passage (the in-shaft passage 31) which corresponds to the operated state and the stopped state of the compressor 10. When the valve body 42 is located in the connecting position, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (suction pressure region) in the compressor 10. When the valve body 42 is located in the disconnecting position, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142. The valve body 42, the return spring 47, the permanent magnet 48 constitute a shifting device 52. The shifting device 52 shifts between the connecting state and the disconnecting state.

In the state shown in FIG. 3, the shifting device 52 is in the disconnecting state where the outlets 312 (as shown in FIG. 1) and 313 of the supply passage are disconnected from the suction chamber 142. In other words, the compression chambers 271, 281 are disconnected from the suction chamber 142 upstream the shifting device 52 through the valve mechanism (the rotary valves 35, 36). In the state shown in FIG. 4, the shifting device 52 is in the connecting state where the outlets 312 (as shown in FIG. 1) and 313 of the supply passage are connected to the suction chamber 142. In other words, the compression chambers 271, 281 are connected to the suction chamber 142 upstream the shifting device 52 through the rotary valves 35, 36.

FIG. 5A shows a graph of torque fluctuation of the compressor 10 with the permanent magnet 48, and a waveform E1 in FIG. 5A indicates the torque fluctuation in the compressor 10 when the compressor 10 is started. FIG. 5B shows a graph of positional change of the valve body 42 in the compressor 10 having the permanent magnet 48, and a line D1 indicates the positional change of the valve body 42. In the graph of FIG. 5A, the horizontal axis represents time, and the vertical axis represents torque. Time T0 represents the time when the electromagnetic clutch 25 is changed from a deactivated state into an activated state. Time T1 represents starting time when the introduction port 441 is exposed to the suction chamber 142, that is, the starting time of communication between the suction chamber 142 and the inner space 442. In the graph of FIG. 5B, the horizontal axis represents time, and the vertical axis represents the position of the valve body 42. Position L1 represents the disconnecting position (the position of the valve body 42 shown in FIG. 3) and position L2 represents the connecting position (the position of the valve body 42 shown in FIG. 4). The difference (T1−T0) represents the elapsed time from the time T0 when the electromagnetic clutch 25 is changed into the activated state, to the time T1 when the communication between the introduction port 441 and the suction chamber 142 is started.

FIG. 5C shows a graph of torque fluctuation of a fixed displacement piston type compressor without the permanent magnet 48, and a waveform E2 in FIG. 5C indicates the torque fluctuation in the compressor when the compressor is started. FIG. 5D shows a graph of positional change of a valve body in the compressor without the permanent magnet 48, and a line D2 indicates the positional change of the valve body. In the graph of FIG. 5C, the horizontal axis represents time, and the vertical axis represents torque. Time T0 represents the time when the electromagnetic clutch 25 is changed from a deactivated state into the activated state. Time T2 represents starting time when the introduction port 441 is exposed to the suction chamber 142, that is, the starting time of communication between the suction chamber 142 and the inner space 442. In the graph of FIG. 5D, the horizontal axis represents time, and the vertical axis represents the position of the valve body. The difference (T2−T0) represents the elapsed time from the time T0 when the electromagnetic clutch 25 is changed into the activated state, to the time T2 when the communication between the introduction port 441 and the suction chamber 142 is started.

According to the first preferred embodiment, the following advantageous effects are obtained.

(1) As shown in the graphs of FIGS. 5A, 5C, the elapsed time (T1−T0) is greater than the elapsed time (T2−T0). When the elapsed time (T1−T0) is greater, sudden torque fluctuation in a short time is effectively reduced in the compressor 10.

The difference between the elapsed time (T1−T0) and the elapsed time (T2−T0) is resulted from whether the compressor 10 has the permanent magnet 48 or not. The magnetic force of the permanent magnet 48 delays the start of the movement of the valve body 42, which is in the disconnecting position at the start of the compressor 10, moving from the disconnecting position to the connecting position. Thereby the elapsed time (T1−T0) is greater than the elapsed time (T2−T0), and as a result, the shock at the start of the compressor 10 is reduced.

Further, the compressed amount of the refrigerant is small during the time when the communication between the suction chamber 142 in the compressor 10 and the introduction port 441 is shut off (that is, the valve body 42 is in the disconnecting position). Thereby the effect reducing the torque fluctuation, or, the shock absorbing effect at the start of the compressor 10 is high.

(2) The valve body 42 is urged by the permanent magnet 48 in addition to the return spring 47 in the direction from the connecting position to the disconnect position. The magnetic force of the permanent magnet 48 which is applied to the valve body 42 is maximum when the valve body 42 is in the disconnecting position. Thereby, the spring force of the return spring 47 for positioning the valve body 42 in the disconnecting position can be reduced, compared to the case where the permanent magnet 48 is not provided.

When the communication between the suction chamber 142 and the introduction port 441 is started, the pressure fluctuation in the supply passage is large, and hunting of the valve body 42 may be easily occurred. Once the valve body 42 is moved apart from the disconnecting position (the position where the valve body 42 is stuck to the permanent magnet 48), the magnetic force of the permanent magnet 48 attracting the valve body 42 toward the disconnecting position is getting to be rapidly reduced. Thereby the movement speed of the valve body 42 is increased after the valve body 42 is moved apart from the permanent magnet 48, compared to the case without the permanent magnet 48. Therefore, even when the fluctuation in the pressure condition in the supply passage is large, the hunting of the valve body 42 is suppressed.

(3) When the compressor 10 is stopped, the valve body 42 is returned to the disconnecting position by the spring force of the return spring 47. Utilizing the return spring 47 results in a simple construction in returning the valve body 42 to the disconnecting position. (4) The valve body 42 is moved in the direction of the rotary axis 210 of the rotary shaft 21. The inner wall surface 401 of the rear housing 14 extends so as to intersect with the movement direction of the valve body 42 (the direction of the rotary axis 210). The inner wall surface 401 of the rear housing 14 is an appropriate position for providing the permanent magnet 48. (5) When the valve body 42 is in the disconnecting position, the valve body 42 is in contact with the permanent magnet 48. The construction where the valve body 42 comes into contact with the permanent magnet 48 is appropriate for increasing the performing force of the permanent magnet 48 which maintains the valve body 42 in the disconnecting position. (6) The valve body 42 in the disconnecting position is maintained at the disconnecting position in the surface contacting state with the permanent magnet 48. The structure where the valve body 42 comes into surface contact with the permanent magnet 48 is appropriate for increasing the performing force of the permanent magnet 48 which maintains the valve body 42 in the disconnecting position. (7) The introduction port 441 as the inlet of the inner space 442 of the valve body 42 is closed in such a manner that the introduction port 441 is located in the inner space 442 when the valve body 42 is in the disconnecting position. The introduction port 441 is exposed to the suction chamber 142 at the outside the inner space 411 when the valve body 42 is at the connecting position. The construction in which the introduction port 441 moves into and away from the inner space 411 is appropriate for ensuring a sufficient cross-sectional area of the supply passage by enlarging the introduction port 441.

A second preferred embodiment of the present invention will now be described with reference to FIGS. 6A, 6B. The same reference numerals denote the identical components to those in the first preferred embodiment.

The rear housing 14 includes a communication chamber 53 and a valve hole 541 formed therein. A plate 55 for opening and closing the valve hole 541 is accommodated in the communication chamber 53. The plate 55 is made of magnetic material. The valve hole 541 is formed through a partition wall 54 which separates the communication chamber 53 from the suction chamber 142. The inlet 311 of the in-shaft passage 31 is formed at the rear end surface 213 of the rotary shaft 21 in the rear cylinder block 12 and is open to the communication chamber 53 in the rear housing 14.

A piston 56 is inserted in the inner space 411. A rod 57 is formed integrally with the piston 56. The plate 55 is fixed to the end of the rod 57. A ring-shaped permanent magnet 58 is fittedly inserted in the partition wall 54 so as to surround the valve hole 541. The permanent magnet 58 has the front and rear surfaces, and a planar valve seat 581 is formed in the front surface of the permanent magnet 58 adjacent to the communication chamber 53. The plate 55 comes into contact with the valve seat 581 for closing the valve hole 541, and moved apart from the valve seat 581 for opening the valve hole 541. A sealing surface 551 of the plate 55 facing the valve seat 581 is formed of a planar shape. In other words, when the valve hole 541 is closed by the plate 55, the sealing surface 551 of the plate 55 is in surface contact with the valve seat 581. The piston 56, the rod 57 and the plate 55 constitute a valve body 59 for opening and closing the valve hole 541. The valve body 59 defines a pressure chamber 412 in the inner space 411.

A return spring 60 is interposed between the piston 56 and the partition wall 54. The return spring 60 urges the piston 56 in the direction to push the piston 56 into the inner space 411. In FIG. 6B, the valve body 59 is in a connecting position connecting the communication chamber 53 to the suction chamber 142 by opening the valve hole 541. In FIG. 6A, the valve body 59 is in a disconnecting position disconnecting the communication chamber 53 from the suction chamber 142 by closing the valve hole 541. The return spring 60 urges the valve body 59 in the direction from the connecting position toward the disconnecting position.

Plural restricting members 552 protrude from the front surface of the plate 55 facing the end surface 213 of the rotary shaft 21. The restricting members 552 come into contact with the rear end of a cylindrical portion 123 protruding from an end surface 122 of the rear cylinder block 12, and are moved away from the rear end of the cylindrical portion 123. In a state where the valve body 59 is in the connecting position as shown in FIG. 6B, the restricting members 552 are in contact with the rear end of the cylindrical portion 123. In a state where the valve body 59 is in the disconnecting position as shown in FIG. 6A, the restricting members 552 are spaced apart from the rear end of the cylindrical portion 123.

When the operation of the compressor 10 is stopped, the valve body 59 is located in the disconnecting position as shown in FIG. 6A due to the spring force of the return spring 60. In this state, the refrigerant in the suction chamber 142 does not flow into the communication chamber 53. When the compressor 10 is started, the refrigerant in the in-shaft passage 31 and the communication chamber 53 is introduced into the compression chambers 271 (shown in FIG. 1) and 281. Due to the suction motion, the pressures in the in-shaft passage 31 and the communication chamber 53 decrease. That is, the pressures in the in-shaft passage 31 and the communication chamber 53 become lower than the pressure in the suction chamber 142. Thereby the valve body 59 is in the connecting position as shown in FIG. 6B, and the refrigerant in the suction chamber 142 flows into the compression chambers 271 (as shown in FIG. 1) and 281 through the valve hole 541, the communication chamber 53 and the in-shaft passage 31.

The valve body 59, the return spring 60, and the permanent magnet 58 constitute a shifting device 52A. The shifting device 52A shifts between a connecting state and a disconnecting state. In the connecting state, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (the suction pressure region) in the compressor 10. In the disconnecting state, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142.

When the valve body 59 is in the disconnecting position, the plate 55 formed of magnetic material is stuck to the permanent magnet 58. Thereby the shock absorbing effect at the start of the compressor 10 is highly obtained in the second preferred embodiment. Further, since the volume of the communication chamber 53 which accommodates the plate 55 is reduced, similar to the first embodiment, the shock absorbing effect is high.

The following will describe a third embodiment of the present invention with reference to FIGS. 7A and 7B. The same reference numerals denote the identical components to those in the first preferred embodiment.

A piston 61 is slidably fitted in the cylindrical portion 41. The piston 61 defines the pressure chamber 412 in the inner space 411. The piston 61 is attracted by the permanent magnet 48 fixed on the inner wall surface 401 of the base portion 40, however, the piston 61 is formed not so as to be in contact with the permanent magnet 48.

A rod 62 is connected to the piston 61. The rod 62 is inserted in an in-shaft passage 31A. The in-shaft passage 31A includes a small-diameter passage 314 and a large-diameter passage 315. A disk 63 is fixed to the front end of the rod 62 in the small-diameter passage 314. A cylindrical body 64 with a circular cross-section is fixed to the rod 62 in the large-diameter passage 315.

The disk 63 is fitted in the small-diameter passage 314 in such a manner that the disk 63 is slidable in the direction of the rotary axis 210 of the rotary shaft 21. The cylindrical body 64 is fitted in the large-diameter passage 315 in such a manner that the cylindrical body 64 is slidable in the direction of the rotary axis 210 of the rotary shaft 21, and that the outlet 313 is to be opened and closed. Part of the in-shaft passage 31A between the disk 63 and the cylindrical body 64 communicates with part of the in-shaft passage 31A between the inlet 311 and the cylindrical body 64 through inner space of the cylindrical body 64.

As shown in FIG. 7B, when the cylindrical body 64 is in a position to close the outlet 313, the disk 63 is located rearward of the outlet 312 in the in-shaft passage 31A. In this state, the refrigerant in the in-shaft passage 31A does not flow into the compression chamber 271 through the outlet 312. As shown in FIG. 7A, when the cylindrical body 64 is in a position to open the outlet 313, the disk 63 is located frontward of the outlet 312 in the in-shaft passage 31A. In this state, the refrigerant in the in-shaft passage 31A flows into the compression chamber 271 through the outlet 312.

A step 316 is formed between the small-diameter passage 314 and the large-diameter passage 315. A return spring 65 is interposed between the step 316 and the cylindrical body 64. The return spring 65 urges the disk 63, the cylindrical body 64, the rod 62 and the piston 61 altogether in the direction toward the pressure chamber 412 so as to push the piston 61 into the inner space 411.

When the compressor 10 is stopped, the disk 63 and the cylindrical body 64 are maintained at the disconnecting position as shown in FIG. 7B by the spring force of the return spring 65. In this state, the piston 61 is slightly apart from the permanent magnet 48.

When the compressor 10 is started, the refrigerant in a space 317 (a part of the in-shaft passage 31A) defined by the disk 63 and the front end of the in-shaft passage 31A is introduced into the compression chamber 271, and the pressure in the space 317 decreases. Thereby the disk 63 and the cylindrical body 64 are moved from the disconnecting position as shown in FIG. 7B toward the connecting position as shown in FIG. 7A to overcome the spring force of the spring 65. When the compressor 10 is stopped, the disk 63 and the cylindrical body 64 are returned to the disconnecting position as shown in FIG. 7B by the spring force of the return spring 65. Thus, the disk 63 and the cylindrical body 64 serve to disconnect the outlets 312, 313 of the supply passage from the suction chamber 142. The disk 63, the cylindrical body 64, the rod 62, and the piston 61 constitute a valve body which defines the pressure chamber 412 in the inner space 411.

The valve body is moved between the connecting position and the disconnecting position in accordance with the pressure in the space 317 (a part of the in-shaft passage 31A, or the supply passage) which corresponds to the operated state and stopped state of the compressor 10. In the connecting position, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (the suction pressure region) in the compressor 10. In the disconnecting position, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142. The valve body, the return spring 65, and the permanent magnet 48 constitute a shifting device 52B. The shifting device 52B shifts between a connecting state and a disconnecting state. In the connecting state, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (suction pressure region) in the compressor 10. In the disconnecting state, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142.

According to the third preferred embodiment, the similar effects as the first preferred embodiment are obtained. Specifically, the third embodiment is more effective than the first and the second embodiments in absorbing the shock at the start of the compressor 10. That is because the refrigerant which is to be introduced into the compression chambers 271, 281 is only in the space 317, outlets 312, 313, and communication passages 32, 33, when the disk 63 and the cylindrical body 64 are in the disconnecting position.

The following will describe a fourth preferred embodiment of the present invention with reference to FIGS. 8A, 8B. The same reference numerals denote the identical components to those in the first preferred embodiment. A permanent magnet 66 is fixed to the piston member 43 of the valve body 42, and a joint plate 67 formed of magnetic material is fixed to the base portion 40.

When the compressor 10 is stopped, the valve body 42 is maintained in the disconnecting position by the spring force of the return spring 47 as shown in FIG. 8A. In this state, the permanent magnet 66 is stuck to the joint plate 67 by the magnetic force.

When the compressor 10 is started, the valve body 42 is moved from the disconnecting position as shown in FIG. 8A to the connecting position as shown in FIG. 8B by overcoming the spring force of the return spring 47 and the attracting force due to the magnetic force of the permanent magnet 66. The valve body 42, the return spring 47, the permanent magnet 66, and the joint plate 67 constitute a shifting device 52C which shifts between a connecting state and a disconnecting state. In the connecting state, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (the suction pressure region) in the compressor 10. In the disconnecting state, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142.

According to the fourth preferred embodiment, the similar effects are obtained as the first preferred embodiment.

The following will describe a fifth preferred embodiment of the present invention with reference to FIG. 9. The same reference numerals denote the identical components to those in the first preferred embodiment.

A piston type compressor 10A is a fixed displacement type and includes a cylinder block 12, a front housing 13, and a rear housing 14 so as to form a compressor housing assembly. A crank chamber 24 is defined in the cylinder block 12 and the front housing 13 so as to accommodate a swash plate 23. Single-headed pistons 68 are engaged with the swash plate 23. The single-headed pistons 68 are reciprocated in cylinder bores 28 in accordance with the rotation of the swash plate 23. A rotary valve 36 is formed in a rotary shaft 21 at a position corresponding to the cylinder block 12. A valve body 42 and a permanent magnet 48 are provided in the rear housing 14.

According to the fifth preferred embodiment, the similar effects are obtained as the first preferred embodiment.

The present invention is not limited to the above-described embodiments, but may be modified into the following alternative embodiments.

The first rotary valve 35 and the second rotary valve 36 may be formed independently from the rotary shaft 21.

In the first embodiment, a ring-shaped permanent magnet may be fitted to the inner circumferential surface of the cylindrical portion 41.

In the first embodiment, only the piston member 43 of the valve body 42 may be formed of magnetic material.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims. 

1. A suction structure for allowing refrigerant from a suction pressure region in a piston type compressor, wherein cylinder bores for accommodating a respective piston are arranged around a rotary shaft, wherein a cam body is formed with the rotary shaft, wherein the piston is engaged with the cam body so that rotation of the rotary shaft is transmitted to the piston, wherein a compression chamber is defined by the piston in the respective cylinder bore, wherein a rotary valve is rotated integrally with the rotary shaft, wherein the rotary valve has a supply passage for introducing the refrigerant from the suction pressure region to the compression chamber, the suction structure comprising: a shifting device for shifting between a connecting state and a disconnecting state, wherein in the connecting state an outlet of the supply passage is connected to the suction pressure region and in the disconnecting state the outlet of the supply passage is disconnected from the suction pressure region, the shifting device including; a valve body movable between a connecting position and a disconnecting position, wherein the connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state; a return spring urging the valve body from the connecting position toward the disconnecting position; and a permanent magnet for attracting the valve body by magnetic force from the connecting position toward the disconnecting position.
 2. The suction structure according to claim 1, wherein the compressor has a housing and the permanent magnet is fixed to the housing.
 3. The suction structure according to claim 2, wherein the valve body is in contact with the permanent magnet when the valve body is in the disconnecting position.
 4. The suction structure according to claim 3, wherein the valve body is in surface contact with the permanent magnet.
 5. The suction structure according to claim 1, wherein the valve body disconnects an inlet of the supply passage from the suction pressure region when the shifting device is in the disconnecting state.
 6. The suction structure according to claim 1, wherein the compressor includes a cylinder block in which the cylinder bores are formed, wherein a rear housing is connected to the cylinder block, wherein a suction chamber as the suction pressure region is formed in the rear housing, wherein the valve body is provided in the rear housing.
 7. The suction structure according to claim 6, the valve body is moved between the connecting position and the disconnecting position in the direction of a rotary axis of the rotary shaft, and wherein the permanent magnet is fixed to an inner wall surface of the rear housing which extends so as to intersect with the movement direction of the valve body.
 8. The suction structure according to claim 1, wherein the compressor has a housing, and the housing includes a communication chamber and a suction chamber, wherein a partition wall separates the communication chamber from the suction chamber, and wherein the permanent magnet is formed with the partition wall.
 9. The suction structure according to claim 1, wherein the valve body includes a piston, a rod, a disk and a cylindrical body, wherein the piston is attracted by the permanent magnet, wherein the rod is connected to the piston, the disk and the cylindrical body, wherein the disk and the cylindrical body disconnect the outlet of the supply passage from the suction pressure region when the shifting device is in the disconnecting state.
 10. The suction structure according to claim 1, wherein the compressor has a housing, and wherein a plate formed of magnetic material is fixed to the housing and the permanent magnet is formed with the valve body so as to be moved to and apart from the plate.
 11. The suction structure according to claim 1, wherein the rotary shaft is connected to an external drive source through a clutch.
 12. A suction structure for allowing refrigerant to flow from a suction pressure region in a piston type compressor, wherein cylinder bores for accommodating a respective piston are arranged around a rotary shaft, wherein a cam body is formed with the rotary shaft, wherein the piston is engaged with the cam body so that rotation of the rotary shaft is transmitted to the piston, wherein a compression chamber is defined by the piston in the respective cylinder bore, wherein a valve mechanism is disposed adjacent to the compression chamber, the suction structure comprising: a shifting device for shifting between a connecting state and a disconnecting state, wherein in the connecting state the compression chamber is connected to the suction pressure region upstream the shifting device through the valve mechanism and in the disconnecting state the compression chamber is disconnected from the suction pressure region upstream the shifting device through the valve mechanism, the shifting device including; a valve body movable between a connecting position and a disconnecting position, wherein the connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state; a return spring urging the valve body from the connecting position toward the disconnecting position; and a permanent magnet for attracting the valve body by magnetic force from the connecting position toward the disconnecting position.
 13. A piston type compressor comprising: a housing; cylinder bores formed in the housing, wherein the cylinder bores are arranged around a rotary shaft; pistons accommodated in the respective cylinder bore; a cam body formed with the rotary shaft, wherein the piston is engaged with the cam body so that rotation of the rotary shaft is transmitted to the piston; a compression chamber defined by the piston in the respective cylinder bore; a rotary valve rotated integrally with the rotary shaft, wherein the rotary valve includes a supply passage for introducing refrigerant from a suction pressure region in the compressor to the compression chamber; and a shifting device for shifting between a connecting state and a disconnecting state, wherein in the connecting state an outlet of the supply passage is connected to the suction pressure region and in the disconnecting state the outlet of the supply passage is disconnected from the suction pressure region, the shifting device including; a valve body movable between a connecting position and a disconnecting position, wherein the connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state; a return spring urging the valve body from the connecting position toward the disconnecting position; and a permanent magnet for attracting the valve body by magnetic force from the connecting position toward the disconnecting position. 